This invention relates to pneumatic tire manufacture and more particularly to a cutting apparatus for cutting ply stock material which is employed in the construction and manufacture of pneumatic tires.
In the manufacture of pneumatic tires, one of the principal members used to build the tire carcass is a thin sheet of uncured rubber-like material known as a fabric, building ply or ply stock. In the manufacture of such ply stock, parallel cords of fabric are passed through a pair of rolls in cooperation with calendering rolls which work and calendar unvulcanized rubber onto the parallel cords as they pass through the pinch rolls to form a continuous sheet with the parallel strands of cord fabric embedded therein and running in direction that is parallel to the longitudinal centerline of the materials. Thereafter, such sheet material is bias cut into sections of fabric which are then spliced together to make a building ply or ply stock with cords therein located at a desired bias angle relative to the longitudinal centerline of the ply stock. Such stock or ply stock may be at 90.degree. angle to the longitudinal centerline of the ply stock formed; however, for purpose of this description and example, the invention will be described wherein the cords are at some small acute angle relative to the longitudinal centerline of the ply stock. Layers of ply stock are applied to a tire building drum in such a manner that cord members of overlapping plies criss-cross with respect to the cord members above or below. The tire beads are then set against the ends of the ply stock and the plies are turned thereover. Additional plies, chafer strips, sidewall strip, breakers, overhead belts and a tread ply may be applied in varying orders, and stitched thereto. Such carcass is substantially a flat band, wherein the angle is measured between the cords and the circumferential line around the crown of the tire. In the case of conventional bias ply pneumatic passenger tires, this may be approximately 60.degree.. However, this apparatus can cut fabric material with wire strands therein which run normal to the direction of conveyance. After the removal of such green tire, the tire is given a toroidal shape during vulcanization or on a second machine prior to vulcanization, wherein the angle after vulcanization may be 30.degree. to 35.degree. in the above example depending on many factors including drum set. The above description has generally referred to tires manufactured from fabric, however, the present invention is also directed to building plies which use non-extensible cord materials such as nylon, kevlar and wire. In the processing of ply stock containing wire, processing has been difficult because of the inherent difficulty in cutting wire, which cutting is particularly compounded by the very low bias angle cutting on such stock wherein the cutters tend to push and displace the wire ends, which action distorts the stock. This apparatus can also cut stock which has zero bias angle.
In bias cutting rubberized cloth fabric, the conventional way of cutting is to use a pair of fingers that lift the fabric away from the conveyor belt on which it travels, so that a rapidly rotating cutter disk above the fingers but cooperative therewith cuts the fabric. The application of this apparatus to rubberized wire fabric including fabric for radial tires is difficult and unsatisfactory. Where the speed of rotation of the rotating cutter is greater than the linear speed of the cutter as it moves across the material to be cut, the tendency is to gather the material due to the action of the rapidly rotating cutter; whereas if the rotational speed is less than the linear speed, the tendency is to push the fabric material ahead of the cutter. The rotating cutter of the present invention has a plurality of circumferentially spaced cutting edges which are linear, giving the cutter a downwardly cutting or shearing action in cooperation with a linearly movable anvil that is supported in its movement to assure a firm cutting action during the shearing cut. Upon the completion of a cut across the fabric material, it is desirable to move the cutter and anvil out of the way so that as the cutter and anvil can be returned to their starting position while the fabric material can be advanced or indexed to the next position in preparation for the succeeding cut.